一种基于改进频域最小均方算法的少模光纤模式复用系统均衡

A modified adaptive least mean square frequency domain algorithm for equalization of mode division multiplexed in few mode fiber transmission

基于少模光纤的模式复用传输在近些年由于其超过单模光纤非线性香农极限的高传输容量而受到广泛关注,同时偏振复用在不改变光纤链路的情况下,使得系统传输容量翻倍.因此模式复用和偏振复用的结合为下一代超100 Gb/s光网络提供了一种可行的解决方案.然而,该系统的性能受到模式耦合和不同模式的群延时的影响.本文主要讨论基于频域最小均方(LMS)算法的数字均衡技术在少模光纤的偏振模式复用系统中的应用,提出了一种以蝶形复数有限冲激响应滤波器为基本结构的改进频域最小均方算法.该算法通过改进在每一频域柜中的平均功率方程来获得更好的均衡效果.仿真结果表明:采用改进频域LMS算法后在收敛效果上优于传统频域LMS算法,同时提高了系统性能.

Mode division muhiplexed （MDM） in few mode fibers has gained attraction due to its potential to achieve ultra-high capacity beyond the nonlinear Shannon limit of the single mode fiber. Meanwhile, polarization di- vision muhiplexing （PDM） can make the system transmission capacity doubled without changing the fiber link.The combination of MDM and PDM can provide much more capacity up to several hundreds Gbit/s.However,it cannot be ignored that the effect of mode coupling and differential mode group delay on optical signals exists in transmis- sion and mitigating these impairments is required in this multiplexing.This paper focuses on the frequency domain least mean square （LMS） digital equalization for MDM with PDM in few mode fiber system. A modified frequency domain LMS algorithm is proposed, which is operated with a butterfly finite impulse response （FIR） filter by means of modifying equations according to average power in each frequency bins.Simulation results show that the modified algorithm can improve the convergence speed and the system performance compared with traditional algorithm.